return the smallest positive difference between elements of an array of numbers

algorithimschallenge.js

var findSmallestDifference = function(arr) {
    var differences = [];
    arr.sort(function(c,d){return c - d});
    for(a=0;a<arr.length;a++){
        for(b=a+1;b<arr.length;b++){
            differences[differences.length] = arr[b] - arr[a];
        } 
    }
    var answer = (differences[0]*2)
    for (e=0;e<differences.length;e++){
            if (differences[e] < differences[e+1]) {
                    var bestOfTwo = differences[e]
                    if (bestOfTwo < answer) {
                        answer = bestOfTwo;
                    }
            }
    }
    return answer;
};
var result = findSmallestDifference([102,10,-1,-6,1000,291892,]);
console.log(result);